add alternative names to aws-acm-cert test (#203)

While poking around to debug an issue I added a bit more test coverage here.

### Test Plan
* CI

### References

aws-acm-cert/module_test.go

@@ -27,8 +27,17 @@ func TestAWSACMCertInitAndApply(t *testing.T) {
 		testutil.UniqueId(),
 		testutil.EnvVar(testutil.EnvRoute53ZoneName))
 
+	alternativeDomainName := fmt.Sprintf(
+		"%s.%s",
+		testutil.UniqueId(),
+		testutil.EnvVar(testutil.EnvRoute53ZoneName))
+
 	route53ZoneID := testutil.EnvVar(testutil.EnvRoute53ZoneID)
 
+	alternativeNames := map[string]string{
+		alternativeDomainName: route53ZoneID,
+	}
+
 	options := testutil.Options(
 		testutil.DefaultRegion,
 		map[string]interface{}{
@@ -37,9 +46,10 @@ func TestAWSACMCertInitAndApply(t *testing.T) {
 			"service": service,
 			"owner":   owner,
 
-			"cert_domain_name":      certDomainName,
-			"aws_route53_zone_id":   route53ZoneID,
-			"validation_record_ttl": 5,
+			"cert_domain_name":               certDomainName,
+			"aws_route53_zone_id":            route53ZoneID,
+			"validation_record_ttl":          5,
+			"cert_subject_alternative_names": alternativeNames,
 		},
 	)
 

aws-acm-cert/variables.tf

@@ -4,7 +4,7 @@ variable "cert_domain_name" {
 }
 
 variable "cert_subject_alternative_names" {
-  type        = map
+  type        = map(string)
   description = "A map of <alternative_domain:route53_zone_id>"
   default     = {}
 }
@@ -48,4 +48,4 @@ variable "subject_alternative_names_order" {
   type        = list(string)
   description = "Order to list the subject alternative names in the ACM cert. Workaround for https://github.com/terraform-providers/terraform-provider-aws/issues/8531"
   default     = null
-}
+}